This invention relates to a rear hub for a bicycle, and more particularly to a rear hub for a bicycle, which has an inner member provided at one axial end of a hub shell and an outer member carrying at least one sprocket and being supported unidirectionally rotatably to the inner member through a cylindrical bearing member having ball races.
Generally, this kind of rear hub is provided at one axial end of the hub shell with the inner member carrying pawls. Onto the outer periphery of the inner member is sleeved the outer member which is provided at its inner periphery with ratchet teeth engageable with the pawls and at the outer periphery with sprockets. A cylindrical bearing member is screwed with the outer periphery of an axially outward end at the inner member and balls are interposed between the cylindrical bearing member and the outer member and between the outer member and the inner member, so that the outer member may be supported unidirectionally rotatably to the inner member.
The outer member conventionally is adjusted in its freely rotating condition in such a manner that one or more adjusting plates are used to adjust the cylindrical bearing member in position screwable with the inner member, the cylindrical bearing member being tightened by a lock nut and fixed at a proper position. Since this adjustment requires one to increase or decrease the number of adjusting plates, it takes a significant amount of time.
Where an error in precision in one or more of the above described members makes it impossible to adjust the outer member in its rotating condition by use of only one adjusting plate, one or more plates should be added after removal of the cylindrical bearing member from the inner member. Thereafter, the cylindrical bearing member should be fixed to the inner member by being rescrewed thereto. Furthermore, balls interposed between the cylindrical bearing member and the outer member escape following the removal of cylindrical bearing member. Hence, the outer member is not only very difficult to adjust in its rotating condition but it is also difficult to assemble. Also, an unbalanced load, if applied to the cylindrical bearing member, causes thrust thereon to move the bearing member slightly axially. As a result, the rotating condition of the outer member or hub shell deteriorates quickly.
In order to overcome the above problems, the present invention has been designed. An object of the invention is to provide a rear hub capable of facilitating adjustment of the outer member in its rotating condition, simplifying an assembly of the outer member, and keeping the outer member and hub shell in proper rotating conditions for a long time even when the cylindrical bearing member is subjected to an unbalanced load.
The present invention is directed to improvements in a rear derailleur for a bicycle, which derailleur has an inner member at one axial end of a hub shell, a cylindrical bearing member mounted on the inner member axially outwardly thereof, and an outer member having at least one sprocket and being supported unidirectionally rotatably to the inner member through a pair of first and second bearings. This invention is characterized in that the inner member has at its axially outward portion a receiving portion for receiving thereon the cylindrical bearing member, the cylindrical bearing member is provided at its central portion with a tubular fitting portion of an inner diameter larger than an outer diameter of the receiving portion, and between the outer periphery of the receiving portion and the inner periphery of the fitting portion is formed an annular space into which a sleeve is press-fit, so that the cylindrical bearing member may be fixed at a desired position on the receiving portion.
In other words, this invention has been designed to improve the conventional screwable fixing of the cylindrical bearing member to the inner member. Instead of the screwable fixing, the cylindrical bearing member is press-fit onto the inner member by use of a sleeve separate from the cylindrical member and inner member, thereby being fixed at a desired position thereon.
In greater detail, the sleeve is formed mainly of synthetic resin, such as diureide compound, or nonferrous metal, such as aluminum or copper. After being press-fit onto the inner member, the cylindrical bearing member is released from a force applied thereto in the direction of press-fitting, and at which time a spring back is generated to fix the cylindrical member at its optimum position to allow the outer member to freely rotate.
The inner member and cylindrical bearing member are usually formed of steel and have a hardened surface to improve their wear-resistance. Hence, a direct press-fit of the cylindrical bearing member onto the inner member will produce cracks thereon. However, the use of a sleeve prevents cracks on both aforesaid members and the aforesaid spring back is utilized to fix the cylindrical bearing member at the optimum position with respect to the inner member. As a result, conventional adjusting plates are not required thereby eliminating the above described problems associated with their use.
These and other objects and novel features of the invention will be more apparent from the description of an embodiment thereof shown in the accompanying drawings.